This project has two basic objectives. First, salient biophysical characteristics of bovine and human cervical mucus will be studied in vitro using nuclear magnetic resonance spectroscopy (NMR) and a new instrument for rheological testing (RER). Cyclic variations in bovine cervical mucus during the oestrus cycle will be quantitatively studied, utilizing discriminant analysis. Second, a prototype RER will be built suitable for mucus assessment in vivo. An initial study using this instrument will be made, utilizing discriminant analysis. Second, a prototype PER will be built suitable for mucus assessment in vivo. An initial study using this instrument will be made, utilizing excised bovine reproductive tracts. Measurements by this instrument, and pH and ionic specific electrodes, will first be made on the mucus in situ, and then, after removal, on the same mucus specimens in vitro.